Industrial mixing, emulsifying, fine cutting processes, particularly for food preparation but also in other industrial fields, are generally aimed at producing stable emulsions of liquid and powder materials, or materials having different viscosities, possibly by crushing of components in solid or lump form and sometimes operating at water or other liquid evaporation temperatures, as well as under modified and controlled atmosphere, to obtain a mix that maintains its organoleptic and physical properties unaltered with time.
A number of product mixing and processing systems are known which are designed for food preparation, ranging from the traditional blender to large stirrers, as also used in the confectionery industry, e.g. for chocolate production. All these mixers are substantially based on the concept of stirring and rotating the material to be processed in a cylindrical container, thereby causing it to hit or at least abut against at least one tool for cutting or mixing it, and thus provide a homogeneously mixed product.
In a long-known prior art technique, a dispersion mixer is provided, which has a cylindrical container, with an axial drive shaft mounted to its upper opening and equipped with axial mixing tools, as well as a secondary drive shaft having a different rotation speed, for rotating other mixing tools cooperating with a lateral scraper, as disclosed in EP 0 048 134, by Burgess, dated 1981.
This solution has proved to involve high power consumption, due to the requirement of supplying power to two separate motors, and to not allow the use of a hermetic sealing lid for modified atmosphere processing.
A first known variation of this solution provides a fixed-container mixer having no central shaft, but a series of peripheral shafts which are rotated by a central sleeve with a crown wheel through appropriate pinions which can impart a high rotation speed to the tools of each shaft, as disclosed in EP 0 096 136 by Couvroit, dated 1982. In this solution, each mixing shaft also has the task of dragging the product into circular motion within the bowl, which requires a great driving force, and no hermetic lid sealing is allowed, for controlled temperature and atmosphere processing.
A more recent technique turned back to the use of a central shaft driving a number of radial mixing tools, as disclosed in EP 0 829 891 by Deboffles, dated 1998 or in EP 0 925 891 by Schneider, dated 1998, which all have a single motor disposed on the outer surface of the bottom of the bowl, ensuring a more balanced power consumption relative to the low number of revolutions of the drive shaft and to the multiplied number of revolutions of each mixing tool. Nevertheless, also in this more recent technique, there is the drawback that the bottom of the bowl cannot be heated, which involves the difficulty of reaching a uniform temperature of the product being processed, and that complex machines are required, having high maintenance requirements.
Yet in another newer technique the control of the central shaft and the mixing shafts is disposed on the lid, with the planetary drive being provided by a single motor, as disclosed in EP 1 719 552 by Tonelli dated 2006, or with two motors acting on container rotation and on tool rotation respectively, as disclosed in EP 2 219 770, by Stahl, dated 2008. While this technique improves the previous one in terms of power consumption, it still suffers from the above mentioned drawbacks, particularly due to the lid-mounted control, which makes it unusable for modified atmosphere processing.
In almost all the above prior art solutions, the provision of two motors involves the problem of a considerable bulk, as well as considerable power requirements, particularly for the mixing tool driving motor, whereby considerable power losses are involved for matching the speeds of the two shafts with the various processes or treatments.
Finally, even in the solutions that use a single driving motor, the complexity of current rotary drive systems causes serious drawbacks in terms of wear and difficult maintenance.